Outbreaks of infection caused by community-acquired methicillin-resistant Staphylococcus aureus in a Canadian correctional facility

Dimensions of poverty as risk factors for antimicrobial resistant organisms in Canada: a structured narrative review

Background

Few studies have assessed the relationship between poverty and the risk of infection with antimicrobial resistant organisms (AROs). We sought to identify, appraise, and synthesize the available published Canadian literature that analyzes living in poverty and risk of AROs.

Methods

A structured narrative review methodology was used, including a systematic search of three databases: MedLINE, EMBASE and Web of Science for articles pertaining to poverty, and infection with AROs in Canada between 1990 and 2020. Poverty was broadly defined to include economic measures and associated social determinants of health. Based on inclusion and exclusion criteria, there were 889 initial articles, and 43 included in the final review. The final articles were extracted using a standard format and appraised using the Joanna Briggs Institute Levels of Evidence framework.

Results

Of 43 studies, 15 (35%) related to methicillin-resistant Staphylococcus aureus (MRSA). One study found a 73% risk reduction (RR 0.27, 95%CI 0.19–0.39, p =  < 0.0001) in community-acquired MRSA (CA-MRSA) infection for each $100,000 income increase. Results pertaining to homelessness and MRSA suggested transmission was related to patterns of frequent drug use, skin-to-skin contact and sexual contact more than shelter contact. Indigenous persons have high rates of CA-MRSA, with more rooms in the house being a significant protective factor (OR 0.86, p = 0.023). One study found household income over $60,000 (OR 0.83, p = 0.039) in univariate analysis and higher maternal education (OR 0.76, 95%CI 0.63–0.92, p = 0.005) in multivariate analysis were protective for otitis media due to an ARO among children. Twenty of 43 (46.5%) articles pertained to tuberculosis (TB). Foreign-born persons were four times more likely to have resistant TB compared to Canadian-born persons. None of the 20 studies used income in their analyses.

Conclusions

There is an association between higher income and protection from CA-MRSA. Mixed results exist regarding the impact of homelessness and MRSA, demonstrating a nuanced relationship with behavioural risk factors. Higher income and maternal education were associated with reduced ARO-associated acute otitis media in children in one study. We do not have a robust understanding of the social measures of marginalization related to being foreign-born that contribute to higher rates of resistant TB infection.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13756-022-01059-1.

Methicillin Resistant Staphylococcus aureus and public fomites: a review

Staphylococcus genus is a Gram-positive coccus normally associated with skin and mucous membranes of warm-blooded animals. It is part of the commensal human microflora, or found in animals, or contaminating surfaces in the community and hospital settings. Staphylococcus aureus is the most pathogenic species belonging to this genus, as it possesses a collection of virulence factors that are expressed solely to evade the immune system. The increase in the misuse of antimicrobial agents predisposed S. aureus to develop antibiotic resistance, including the resistance to methicillin which led to the emergence of Methicillin-Resistant S. aureus (MRSA). MRSA is considered one of the most dangerous nosocomial pathogens causing many hard to treat infections in hospitals and was named as Hospital Associated MRSA (HA-MRSA). Over the past 20-25 years, MRSA was isolated from community settings and thus Community Associated MRSA (CA-MRSA) has emerged. Inside hospitals, MRSA has been isolated from fomites in contact with patients, as well as staff's protective and personal items. This review highlights the worldwide prevalence of MRSA on fomites within the contexts of hospital and community settings.

Outcomes of hip and knee total joint arthroplasty in a Canadian inmate population over a 10-year period

Background

Little information exists regarding the risk of complications in inmates who receive total hip or knee arthroplasties in Canada. Inmates tend to be less healthy owing to socioeconomic factors and an increased number of medical and psychiatric comorbidities. We compared revision and complication rates of total joint replacements in a cohort of incarcerated Canadians versus a cohort of non-inmates.

Methods

We obtained a list of all Canadian inmate inpatient hospital visits with diagnostic/procedure codes of primary hip or knee arthroplasty within the last 10 years from our institution’s discharge abstract database. Demographic data and information related to the perioperative course, along with any data related to postoperative complications/readmissions, were obtained through manual chart review.

Results

The inmate group consisted of 20 men (mean age 58 yr) with a total of 24 primary total joint arthroplasties; the comparison group included 171 men (mean age 62 yr). Postoperatively, the inmates had a 4-fold increased risk of major complication compared with non-inmates (33.3% v. 7.6%; odds ratio 4.21, p = 0.01). The inmates’ revision rate was 20.8% compared with 5.8% in the comparison group (p = 0.03). The most common cause for revision in the inmate group was infection, with a rate of 16.7% compared with 3.5% in the comparison group (p = 0.03).

Conclusion

Patients requiring total joint arthroplasty who are inmates in the Canadian penitentiary system are at increased risk of complication and revision surgeries following total joint arthroplasty.

Community-associated methicillin-resistant Staphylococcus aureus: prevalence in skin and soft tissue infections at emergency departments in the Greater Toronto Area and associated risk factors

Objective:

Community-associated methicillin-resistantStaphylococcus aureus(CA-MRSA), which is caused primarily by the Canadian methicillin-resistantStaphylococcus aureus-10 (CMRSA-10) strain (also known as the USA300 strain) has emerged rapidly in the United States and is now emerging in Canada. We assessed the prevalence, risk factors, microbiological characteristics and outcomes of CA-MRSA in patients with purulent skin and soft tissue infections (SSTIs) presenting to emergency departments (EDs) in the Greater Toronto Area.

Methods:

Patients withStaphylococcus aureusSSTIs who presented to 7 EDs between Mar. 1 and Jun. 30, 2007, were eligible for inclusion in this study. Antimicrobial susceptibilities and molecular characteristics of MRSA strains were identified. Demographic, risk factor and clinical data were collected through telephone interviews.

Results:

MRSA was isolated from 58 (19%) of 299 eligible patients. CMRSA-10 was identified at 6 of the 7 study sites and accounted for 29 (50%) of all cases of MRSA. Telephone interviews were completed for 161 of the eligible patients. Individuals with CMRSA-10 were younger (median 34 v. 63 yr,p= 0.002), less likely to report recent antibiotic use (22% v. 67%,p= 0.046) or health care–related risk factors (33% v. 72%,p= 0.097) and more likely to report community-related risk factors (56% v. 6%,p= 0.008) than patients with other MRSA strains. CMRSA-10 SSTIs were treated with incision and drainage (1 patient), antibiotic therapy (3 patients) or both (5 patients), and all resolved. CMRSA-10 isolates were susceptible to clindamycin, tetracycline and trimethoprimsulfamethoxazole.

Conclusion:

CA-MRSA is a significant cause of SSTIs in the Greater Toronto Area, and can affect patients without known community-related risk factors. The changing epidemiology of CA-MRSA necessitates further surveillance to inform prevention strategies and empiric treatment guidelines.

Prevalence of methicillin-resistant Staphylococcus aureus in skin and soft tissue infections in patients presenting to Canadian emergency departments

Background:

Community-associated methicillin-resistantStaphylococcus aureus(MRSA) is an increasingly common cause of skin and soft tissue infection (SSTI) worldwide. The prevalence of MRSA in SSTIs across Canada has not been well described. Studies in the United States have shown significant geographic variability in the prevalence of MRSA. This study characterizes the geographic prevalence and microbiology of MRSA in patients presenting to Canadian emergency departments with SSTIs.

Methods:

Using a prospective, observational design, we enrolled patients with acute purulent SSTIs presenting to 17 hospital emergency departments and 2 community health centres (spanning 6 Canadian provinces) between July 1, 2008, and April 30, 2009. Eligible patients were those whose wound cultures grewS. aureus. MRSA isolates were characterized by antimicrobial susceptibility testing and pulsed-field gel electrophoresis. All patients were subjected to a structured chart audit, and patients whose wound swabs grew MRSA were contacted by telephone to gather detailed information regarding risk factors for MRSA infection, history of illness, and outcomes.

Results:

Of the 1,353S. aureus–positive encounters recorded, 431 (32%) grew MRSA and 922 (68%) wounds grew methicillin-susceptibleS. aureus. We observed significant variation in both the prevalence of MRSA (11–100%) and the proportion of community-associated strains of MRSA (0– 100%) across our study sites, with a significantly higher prevalence of MRSA in western Canada.

Interpretation:

MRSA continues to emerge across Canada, and the prevalence of MRSA in SSTIs across Canada is variable and higher than previously expected.

Molecular epidemiology and antimicrobial susceptibility profiles of methicillin-resistant Staphylococcus aureus blood culture isolates: results of the Quebec Provincial Surveillance Programme

The objectives of this study were to characterize methicillin-resistant Staphylococcus aureus (MRSA) blood culture isolates and to determine their relative importance in both nosocomial and community-acquired infections. A total of 535 MRSA blood culture isolates were analysed. In vitro susceptibility to 14 agents was determined. The genes nuc, mecA and coding for PVL toxin were identified by PCR. All isolates were characterized by PFGE or spa typing to assess their genomic relationships. Most MRSA isolates were retrieved from nosocomial bloodstream infections (474, 89%) and were of the CMRSA2 genotype. Healthcare-associated (HA)-MRSA bloodstream infections were associated with older age (70-89 years, P = 0·002) and most often secondary to central line infections (P = 0·005). Among MRSA strains associated with community-acquired (CA)-MRSA, 28·8% were isolated in intravenous drug users. CA-MRSA genotypes were more frequently found in young adults (20-39 years, P < 0·0001) with skin/soft tissue as the primary sources of infection (P = 0·006). CMRSA10 genotype was the predominant CA-MRSA strain. All MRSA isolates were susceptible to doxycycline, tigecycline, trimethoprim/sulfamethoxazole and vancomycin. Both the presence of the genes coding for PVL toxin (89·8%) and susceptibility to clindamycin (86·5%) were predictive of CA-MRSA genotypes. Whereas in the USA, HA-MRSA have been replaced by USA300 (CMRSA10) clone as the predominant MRSA strain type in positive blood cultures from hospitalized patients, this phenomenon has not been observed in the province of Quebec.

Hand and nasal carriage of discordant Staphylococcus aureus isolates among urban jail detainees

In 928 Dallas County Jail detainees, nasal carriage of Staphylococcus aureus was found in 32.8% (26.5% methicillin-susceptible Staphylococcus aureus [MSSA] and 6.3% methicillin-resistant S. aureus [MRSA]), and hand carriage was found in 24.9% (20.7% MSSA and 4.1% MRSA). Among MRSA nasal carriers, 41% had hand MRSA carriage; 29% with hand MRSA carriage had no nasal S. aureus carriage. The prevalence of carriage was not associated with duration of the jail stay up to 180 days.

Emergence of new CMRSA7/USA400 methicillin-resistant Staphylococcus aureus spa types in Alberta, Canada, from 2005 to 2012

Methicillin-resistant Staphylococcus aureus (MRSA) has become one of the most significant pathogens affecting global public health and health care systems. In Canada and the United States, the spread of MRSA is primarily attributed to a single dominant epidemic clone: CMRSA10/USA300. Despite this, the CMRSA7/USA400 epidemic clone has been reported to be the predominate epidemic clone in several Canadian provinces and some parts of the United States. This study examined the epidemiology of CMRSA7/USA400 MRSA in Alberta, Canada, from June 2005 to December 2012. Molecular characterization of CMRSA7/USA400 isolates was done using spa, SCCmec, PVL, and PFGE typing and identified two predominant spa types in Alberta: t128 and t1787. Although closely related, these spa types have distinct geographic distributions. From 2010 to 2012, the number of t128 infections has remained stable while there has been a nearly 3-fold increase in the number of provincial t1787 infections, accompanied by 10-fold increases in t1787 infection rates in some communities. Most t128 and t1787 patients were First Nations or Inuit people, and isolates were usually from skin and soft tissue infections in outpatients. t128 patients were significantly older than t1787 patients. Antimicrobial susceptibility testing showed higher mupirocin resistance in t1787 than in t128 MRSA. Improved strategies to reduce or stabilize t1787 infections in Alberta are needed.

Outbreak of Skin Infections Due to Panton-Valentine Leukocidin-Positive Methicillin-Susceptible Staphylococcus aureus in a French Prison in 2010-2011

Background. An outbreak of PVL-positive MSSA skin and soft tissue-infections (SSTIs) was suspected in May 2010 when recurrent SSTI was diagnosed in an inmate of a large prison in Nantes, France. Methods and findings. Retrospective and prospective investigations were performed. Microbiological characterisation was by DNA microarray testing (S. aureus genotyping - Identibac, Alere). We identified 14 inmates meeting our clinical and microbiological case definition for PVL-MSSA SSTI between March 2010 and April 2011. The SSTIs developed in tattooed areas in 4 patients and in areas shaved daily with a mechanical razor in 4 other patients. All case isolates exhibited a similar SmaI pulsed-field gel electrophoresis pattern. Microarray analysis showed that all 14 isolates harboured genes encoding PVL and enterotoxins (A, H, K, and Q) and belonged to clonal complex 1 (CC1). Individual and collective hygiene measures, education delivered to inmates and prison employees, and antibiotic treatment of SSTIs were successful in controlling the outbreak. No new cases were identified after April 2011. Routine screening for PVL-positive MSSA carriage was not feasible. Conclusions. Our data suggest that tattooing and shaving with mechanical razors may constitute risk factors for SSTIs among previously colonised inmates and contribute to the PVL-MSSA outbreak in the prison. Allowing inmates access to professional tattooists and to the hygiene and safety conditions available to people in the community would help to prevent tattoo-related infections.

Community-acquired methicillin-resistant Staphylococcus aureus from skin and soft tissue infections (in a sample of Egyptian population): analysis of mec gene and staphylococcal cassette chromosome

BACKGROUND

Staphylococcus aureus has been recognized as an important pathogen associated with inpatients and community infections. Community-acquired methicillin-resistant S. aureus (CA-MRSA) infections commonly present as skin and soft-tissue infections (SSTIs). Treatment often includes incision and drainage with or without adjunctive antibiotics.

OBJECTIVES

This study aimed to identify CA-MRSA infections both phenotypically and genotypically, to determine their spectrum of antibiotic resistance, and to establish the best scheme for molecular distinction between hospital-acquired MRSA (HA-MRSA) and CA-MRSA by staphylococcal cassette chromosome mec (SCCmec) typing and detection of Panton Valentine leukocidin (PVL).

MATERIALS

50 swabs, from skin and soft tissue of infected lesions of outpatients attending the dermatology department of the Medical School, Alexandria University, were collected. Additionally, a nasal swab was taken from every participant.

METHODS

Collection of swabs from the infected skin and soft tissues, followed by laboratory testing to phenotypically and genotypically identify MRSA. Also, nasal swabs were taken from every patient to identify MRSA colonization.

RESULTS

Staphylococcus aureus strains were identified in 38 (76%) of the 50 clinical isolates. 18 (47.37%) out of the 38 S. aureus strains were resistant to oxacillin and cefoxitin discs, were penicillin binding protein 2a (PBP2a) producers, and were initially diagnosed as MRSA. All of the 18 strains were definitively diagnosed as MRSA by mecA gene detection using real time PCR, while only six (33.33%) strains were PVL positive. Using the sets of primers of Zhang et al.: nine (50%) out of the 18 CA-MRSA strains were SCCmec type V, and one (5.56%) was SCCmec type IVc. Then, using the set of primers by Oliveira et al., two (25%) out of the eight untypable MRSA strains were found to be SCCmec type IV, and six (75%) remained untypable.

CONCLUSIONS

CA-MRSA must be considered when treating skin and soft tissue infections, especially in developing countries. Empirical use of agents active against CA-MRSA is warranted for patients presenting with serious SSTIs.

Community-associated methicillin-resistant Staphylococcus aureus infections in men who have sex with men: A case series

BACKGROUND

The purpose of the present study was to describe the clinical characteristics and management of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections among a cohort of men who have sex with men.

PATIENTS AND METHODS

A retrospective chart review was conducted of patients with culture-proven MRSA at Maple Leaf Medical Clinic (Toronto, Ontario) between November 2004 and December 2005. Cases were identified by individual physicians and by queries in the clinical management system. A standard data collection form was used to record patient demographics, potential risk factors for MRSA and course of illness. When available, antimicrobial sensitivities were recorded. DNA fingerprinting using pulsed-field gel electrophoresis, and genetic analysis for SCCmec typing and detection of the Panton-Valentine leukocidin cytotoxin were performed on six available isolates.

RESULTS

Seventeen patients with MRSA infection were identified, 12 (71%) of whom were HIV-positive. The most common clinical presentation was abscess (35%), followed by furuncle (17%), folliculitis (17%), cellulitis (17%) and sinusitis (12%). The majority of MRSA isolates were resistant to ciprofloxacin (92%) and levofloxacin (77%). All isolates were susceptible to trimethoprim-sulfamethoxazole, rifampin, linezolid, gentamicin and clindamycin, while the majority were susceptible to tetracycline (80%). All six isolates tested were SCCmec type IVa-positive and Panton-Valentine leukocidin-positive, and had fingerprint patterns consistent with the CMRSA-10 (USA300) clone.

CONCLUSION

The present study describes the clinical presentation and management of CA-MRSA infections occurring in Toronto among men who have sex with men. The infections appear to have been caused by CMRSA-10, which has caused the majority of CA-MRSA outbreaks elsewhere.

Prevalence of methicillin-resistant Staphylococcus aureus in a Canadian inner-city shelter

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) colonization is increasingly of concern in community settings. However, despite a recent outbreak in Calgary, Alberta, data on the prevalence of MRSA in Canadian communities are lacking. Globally, few studies have been performed in high-risk groups such as inner-city populations.

METHODS

A cross-sectional study of the prevalence of MRSA among residents and staff at three Ottawa, Ontario, shelters was conducted. All participants completed a questionnaire, and provided nasal swabs as well as one of rectal, anal or groin swabs.

RESULTS

Among 84 participants, the prevalence of MRSA colonization was 2.4%. Among the resident subgroup, the prevalence was 4.5%, while no MRSA isolates were found among 40 staff participants. All isolates were USA100 (CMRSA-2) subtypes.

CONCLUSIONS

The prevalence of MRSA colonization among residents is higher than baseline population rates, but is consistent with other inner-city populations. Although community outbreaks of USA300 and USA400 strains are increasingly reported, movement of nosocomial strains (ie, USA100 [CMRSA-2]) into communities remains an important avenue in the spread of MRSA and underscores the importance of nosocomial MRSA control.

A nosocomial outbreak of community-associated methicillin-resistant Staphylococcus aureus among healthy newborns and postpartum mothers

BACKGROUND

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has increasingly been isolated from individuals with no predisposing risk factors; however, such strains have rarely been linked to outbreaks in the hospital setting. The present study describes the investigation of an outbreak of CA-MRSA that occurred in the maternal-newborn unit of a large community teaching hospital in Toronto, Ontario.

METHODS

Screening and clinical specimens collected from mothers and newborns delivered during the outbreak period, as well as from staff on the affected unit, were submitted for microbiological testing. Computerized delivery logs and nursing notes were reviewed, and a case control study was conducted.

RESULTS

Analysis by pulsed-field gel electrophoresis revealed 38 babies and seven mothers with MRSA colonization and/or infection by the same unique strain (Canadian MRSA-10-related) from September to December 2004. Isolates were characterized as having the staphylococcal chromosome cassette mec type IVa and were positive for the Panton-Valentine leukocidin gene. No one health care worker was associated with all cases; however, mothers and newborns exposed to one particular nurse (Nurse A) were almost 23 times (odds ratio 22.7, 95% CI 3.3 to 195.9) more likely to acquire MRSA than those with no such contact. MRSA was successfully isolated from Nurse A and from an environmental swab of a telephone recently used by Nurse A; both isolates matched the pulsed-field gel electrophoresis pattern of the outbreak strain.

CONCLUSION

The first nosocomial outbreak of CA-MRSA among healthy newborns and postpartum mothers in Canada is described. Effective control of sustained MRSA transmission within an institution may require prompt identification, treatment and monitoring of colonized and/or infected staff.

Risk factors for infection and colonization with community-associated methicillin-resistant Staphylococcus aureus in the Los Angeles County jail: a case-control study

BACKGROUND

Community-associated methicillin-resistant Staphylococcus aureus (MRSA) infections and outbreaks occur in correctional facilities, such as jails and prisons. Spread of these infections can be extremely difficult to control. Development of effective prevention protocols requires an understanding of MRSA risk factors in incarcerated persons.

METHODS

We performed a case-control study investigating behavioral risk factors associated with MRSA infection and colonization. Case patients were male inmates with confirmed MRSA infection. Control subjects were male inmates without skin infection. Case patients and control subjects completed questionnaires and underwent collection of nasal swab samples for culture for MRSA. Microbiologic analysis was performed to characterize recovered MRSA isolates.

RESULTS

We enrolled 60 case patients and 102 control subjects. Of the case patients, 21 (35%) had MRSA nasal colonization, compared with 11 control subjects (11%) (P .001). Among MRSA isolates tested, 100% were the USA300 strain type. Factors associated with MRSA skin infection included MRSA nares colonization, lower educational level, lack of knowledge about "Staph" infections, lower rate of showering in jail, recent skin infection, sharing soap with other inmates, and less preincarceration contact with the health care system. Risk factors associated with MRSA colonization included antibiotic use in the previous year and lower rate of showering.

CONCLUSIONS

We identified several risks for MRSA infection in male inmates, many of which reflected preincarceration factors, such as previous skin infection and lower educational level. Some mutable factors, such as showering frequency, knowledge about Staph, and soap sharing, may be targets for intervention to prevent infection in this vulnerable population.

Community-associated methicillin-resistant Staphylococcus aureus: epidemiology and clinical consequences of an emerging epidemic

Staphylococcus aureus is an important cause of skin and soft-tissue infections (SSTIs), endovascular infections, pneumonia, septic arthritis, endocarditis, osteomyelitis, foreign-body infections, and sepsis. Methicillin-resistant S. aureus (MRSA) isolates were once confined largely to hospitals, other health care environments, and patients frequenting these facilities. Since the mid-1990s, however, there has been an explosion in the number of MRSA infections reported in populations lacking risk factors for exposure to the health care system. This increase in the incidence of MRSA infection has been associated with the recognition of new MRSA clones known as community-associated MRSA (CA-MRSA). CA-MRSA strains differ from the older, health care-associated MRSA strains; they infect a different group of patients, they cause different clinical syndromes, they differ in antimicrobial susceptibility patterns, they spread rapidly among healthy people in the community, and they frequently cause infections in health care environments as well. This review details what is known about the epidemiology of CA-MRSA strains and the clinical spectrum of infectious syndromes associated with them that ranges from a commensal state to severe, overwhelming infection. It also addresses the therapy of these infections and strategies for their prevention.

Methicillin-resistant Staphylococcus aureus in Canada: a historical perspective and lessons learned

The history of methicillin-resistant Staphylococcus aureus (MRSA) in Canada has many similarities to MRSA evolution worldwide, but especially to that in the United States and United Kingdom. Reports of MRSA occurred as early as 1964, and community isolates were cited in the 1970s. Nosocomial outbreaks were becoming common by 1978 and flourished gradually thereafter. Endemic institutional MRSA became predominant in the 1990s, threatening large teaching hospitals in particular. In the last decade, both hospital-acquired and community-acquired MRSA have created major medical problems in Canada. More recently, an epidemic of Canadian community-acquired MRSA-10, has led to heightened public health concerns. Canadian contributions to MRSA science are numerous, with organized surveillance continuing to mature across the nation. A typing system for epidemic clones is now available and is being judiciously applied. Estimated costs for MRSA surveillance, treatment, and control are extraordinary, paralleling the dramatic rise in the number of MRSA isolations. Whereas surveillance continues to form an essential aspect of MRSA management, control, eradication, and overall diminution, MRSA reservoirs deserve much greater attention. Such efforts, however, must be as widely publicized in the community and in patient homes as they are in medical institutions responsible for both acute and long-term care.

The human nasal microbiota and Staphylococcus aureus carriage

Background

Colonization of humans with Staphylococcus aureus is a critical prerequisite of subsequent clinical infection of the skin, blood, lung, heart and other deep tissues. S. aureus persistently or intermittently colonizes the nares of ∼50% of healthy adults, whereas ∼50% of the general population is rarely or never colonized by this pathogen. Because microbial consortia within the nasal cavity may be an important determinant of S. aureus colonization we determined the composition and dynamics of the nasal microbiota and correlated specific microorganisms with S. aureus colonization.

Methodology/Principal Findings

Nasal specimens were collected longitudinally from five healthy adults and a cross-section of hospitalized patients (26 S. aureus carriers and 16 non-carriers). Culture-independent analysis of 16S rRNA sequences revealed that the nasal microbiota of healthy subjects consists primarily of members of the phylum Actinobacteria (e.g., Propionibacterium spp. and Corynebacterium spp.), with proportionally less representation of other phyla, including Firmicutes (e.g., Staphylococcus spp.) and Proteobacteria (e.g. Enterobacter spp). In contrast, inpatient nasal microbiotas were enriched in S. aureus or Staphylococcus epidermidis and diminished in several actinobacterial groups, most notably Propionibacterium acnes. Moreover, within the inpatient population S. aureus colonization was negatively correlated with the abundances of several microbial groups, including S. epidermidis (p = 0.004).

Conclusions/Significance

The nares environment is colonized by a temporally stable microbiota that is distinct from other regions of the integument. Negative association between S. aureus, S. epidermidis, and other groups suggests microbial competition during colonization of the nares, a finding that could be exploited to limit S. aureus colonization.

A comparison of risk factors associated with community-associated methicillin-resistant and -susceptible Staphylococcus aureus infections in remote communities

In this case-control study, cases [community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA), n=79] and controls [community-associated methicillin-susceptible S. aureus (CA-MSSA), n=36] were defined as a laboratory-confirmed infection in a patient with no previous hospital-associated factors. Skin and soft tissue were the predominant sites of infection, both for cases (67·1%) and controls (55·6%). Most of the cases (79·7%) and controls (77·8%) were aged <30 years. Investigations did not reveal any significant statistical differences in acquiring a CA-MRSA or CA-MSSA infection. The most common shared risk factors included overcrowding, previous antibiotic usage, existing skin conditions, household exposure to someone with a skin condition, scratches/insect bites, and exposure to healthcare workers. Similar risk factors, identified for both CA-MRSA and CA-MSSA infections, suggest standard hygienic measures and proper treatment guidelines would be beneficial in controlling both CA-MRSA and CA-MSSA in remote communities.

Long-term follow-up of methicillin-resistant Staphylococcus aureus molecular epidemiology after emergence of clone USA300 in San Francisco jail populations

We performed a longitudinal analysis of 502 unique methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates originating from San Francisco jail inmates between 2000 and 2007. Strain USA300, first encountered in 2001, accounted for 82.1% (412/502) of MRSA infections. Non-USA300 MRSA strains were rarely found after 2005 (one isolate in 2006, three in 2007).

Evidence-based approach to abscess management

OBJECTIVE

To provide family physicians with an overview of the evidence for managing superficial cutaneous abscesses.

SOURCES OF INFORMATION

PubMed (from 1950), EMBASE (from 1974), The Cochrane Library (from 1966), and Google (from 1998) were searched as were reference lists of identified articles. Summary sites, such as ACP Journal Club and InfoPOEMs, and background resources were also reviewed.

MAIN MESSAGE

There are many areas of debate regarding abscess management, including pain control, necessity of culture and sensitivity testing, empiric treatment with antibiotics, and open versus primary closure of wounds. Usefulness of cultures and empiric antibiotic treatment has risen to the forefront with the increasing incidence of community-acquired, methicillin-resistant Staphylococcus aureus.

CONCLUSION

In immunocompetent patients with no confounding risk factors, incision and drainage under local anesthetic is generally sufficient for abscess management. There is no compelling evidence for routine cultures or empiric treatment with antibiotics. Further research is required.

A sentinel fatal paediatric case of community-associated methicillin-resistant Staphylococcus aureus in Canada

Community-associated methicillin-resistant Staphylococcus aureus is an established pathogen in many centres in the United States, but has yet to establish a firm foothold in Canada. In the present article, the authors report, to their knowledge, Canada's first fatal paediatric case of invasive disease due to community-associated methicillin-resistant S aureus and review its pathogenesis, epidemiology and treatment.

Methicillin-resistant Staphylococcus aureus: A public health issue with economic consequences

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) has become endemic worldwide in hospitals, and community-associated MRSA is spreading into the community at large.

OBJECTIVES

To estimate the current cost of MRSA in Canada and to assess the magnitude of this public health issue.

METHODS

An extensive review of the literature was conducted to gather epidemiology, health care resource utilization and cost data for MRSA in Canadian settings. The current MRSA burden was estimated using available cost data and the most recent epidemiology data.

RESULTS

The rate of MRSA in Canadian hospitals increased from 0.46 to 5.90 per 1000 admissions between 1995 and 2004, while community-associated MRSA continued to spread into the community. Patients harbouring MRSA required prolonged hospitalization (average 26 days of isolation per patient), special control measures, expensive treatments and extensive surveillance. Total cost per infected MRSA patient averaged $12,216, with hospitalization being the major cost driver (81%), followed by barrier precautions (13%), antimicrobial therapy (4%) and laboratory investigations (2%). The most recent epidemiological data, combined with available cost data, suggest that direct health care cost attributable to MRSA in Canada, including cost for management of MRSA-infected and-colonized patients and MRSA infrastructure, averaged $82 million in 2004 and could reach $129 million in 2010.

CONCLUSION

MRSA is a costly public health issue that needs to be tackled if the growing burden of this disease in Canadian hospitals and in the community is to be limited.